1. Field of the Invention
The present invention is related to a method of manufacturing a blow-molded article having an integral airbag door. More specifically, the present invention is directed to manufacturing an automotive instrument panel having an integral airbag door by simultaneously extruding the one or parison layers and blow-molding the layers to form the panel.
2. Description of the Related Arts
Modern automotive interiors utilize instrument panels that provide a soft touch feel. These instrument panels are usually formed by laminating a flexible skin to a rigid substrate. Many of these processes also included placing a foam material between the skin and substrate to provide a soft-touch feel. These instrument panels have been formed by injection molding one or more of the components of the instrument panel. While injection molding provides design flexibility, it generally requires expensive equipment and tools and does not form an article that has a hollow core.
Another trend among automobile interiors are instrument panels that have a seamless covering over an airbag door. The decorative layer of the instrument panel is used to conceal the airbag door. These instrument panels and made of the usual injection molded construction. A opening path is formed in the substrate, cover and foam to enable the door to open when the airbag is initiated. This construction provides a decorative, seamless appearance, but requires complex and expensive assembly steps for the various components of the instrument panel and airbag door.
It is also known to manufacture hollow articles by blow-molding. These articles utilize a parison extruded between two molds. The parison is inflated to cause the parison to conform to the mold walls. Among the articles that may be made using this process are instrument panels for automobiles. Japanese Patent Application Number 04-283977, filed Sep. 29, 1992, teaches molding a three-layer instrument panel using a skin layer, a foaming body intermediate layer and a base member layer. The skin layer is composed of an olefin thermoplastic elastomer composition. The intermediate layer is composed of a propylene polymer foaming body having a melt tension at 230.degree. C. of 2-20 g. The base member layer is composed of a propylene polymer containing 10-50% by weight of a granular filler or a fibrous filler. The three layer structure is integrally molded into an instrument panel by a multi-layer blow-molding apparatus. The method and construction taught by this application is limited to a simple instrument panel structure that does not includes an integral airbag door or reinforcement supports strengthening the instrument panel.
U.S. Pat. No. 5,328,651 ('651), teaches a method of blow-molding a covering and foam backing for an automotive instrument panel. The skin and foaming material are co-extruded in a blow-molding apparatus and formed into the shaped to conform to an instrument panel. The skin and foam are then bonded to a rigid substrate that was conventionally molded. The process taught by the '651 patent is limited to forming the skin and an foam layers of the instrument panel. The underlying rigid supporting substrate is not formed by blow-molding and the instrument panel is not integrally formed.
It is desirable to form an instrument panel that utilizes blow-molding to form the outer decorative skin layer, intermediate foam layer and underlying substrate layer in a single operation. It is also desirable that the molding operation simultaneously form a concealed door within the instrument panel. The door maybe used to cover an airbag. It is also desirable that the molding operation form the instrument panel to have hollow or channel sections. The hollow or channel sections provide stiffening and rigidity to the instrument panel and allow for air or structural members to pass through the instrument panel.
These and other disadvantages are overcome by the present invention.